Electron beam tube



Oct 7, 1939- A. w. VINGERHOETS ET AL 2,176,599

ELECTRON BEAM TUBE Filed April 10, 1937 :IIIIYIIHIII! IIIIIIIIIEIIIJEIII! V ELAU 1 'l 40 W47. Will/mm wn', M

.INVENTORS ANTON/U5 M. V/NGERHOETSAND ADRIANUSJWMVANOVERBEEK ATTORNEY Patented Oct. 17, 1939 ELECTRON BEAM TUBE Antonius W. Vingerhoets and Adrianus J. W. M.

van Overbeek, Eindhoven, Netherlands, assignors to N. V. Philips Gloeilampenfabrieken Application April 10, 1937, Serial No. 136,034 In Germany April 23, 1936 5 Claims.

This invention relates to a device comprising an electric discharge tube, particularly for amplifying, producing, rectifying or controlling electric oscillations, in which the electrons emanating from the cathode are united to form a beam which is given a deflection by electrostatic means with the aid of a number of deflection plates.

In the conventional tubes having an electron beam, particularly for the above-mentioned purposes, the electrons emanating from the cathode can be united by means of one or more electron lenses to form a beam which, under the influence of a potential difierence between the cathode and one or more other electrodes traverses a large part of the tube and finally strikes the anode or anodes. While traversing the tube the beam passes a number of deflection plates which in the conventional tubes are given a positive voltage relative to the cathode. These deflection plates have supplied to them in addition an alternating voltage which causes a lateral deflection of the electron beam and in this way may bring about current variations at the anode or anodes. In these conventional tubes a current may flow to the deflection plates, which renders very difficult, if not impossible, the use of such tubes for purposes other than low frequency amplification, since, due to the occurrence of the deflection plate current, such a high attenuation is set up in a high frequency oscillatory circuit used in connection with tube that good results cannot be obtained. This attenuation is intensified by the impingement of primary electrons causing sec- .ondary electrons to be dislodged from the deflection plates.

The flow ofcurrent from the beam to the deflection plates occurs and its effects appear not only at a maximum deflection of the beam, but also when an alternating voltage is not supplied to the deflection plates and the beam is at rest and in the axis of the tube because in spite of the satisfactory concentration of the electron stream which emanates from the cathode, there are always free electrons which are not confined to the beam and which may be attracted by the deflection plates, since the latter are always given a positive potential relative to the cathode.

The principal object of our invention is to provide an improved electron discharge device of the type having an electron beam deflected by deflection plates in which difliculties due to flow of current to the deflection plates are avoided.

In a device constructed according to our present invention, and comprising an electric discharge tube particularly for amplifying, producemanating from the cathode is concentratedinto a beam by an accelerating or suction anode at high positive potential, it is known to be very desirable, if not necessary, to arrange on that side of the accelerating or focusing anode which is remote from the cathode, an auxiliary means, for example an electron lens, to obtain further concentration of the beam and optimum conditions, particularly with respect to amplification. Although for this purpose it is possible to arrange between the accelerating or focusing anode and the deflection plates and/or between the deflection plates and the output anode or anodes of the tube one or more plate-shaped electron lenses, a simpler construction is to form an electron lens directly between the accelerating or focusing anode and the deflection plates by giving to the deflection plates a voltage which is but slightly negative relative to the accelerating anode, although the result is that the potential of the deflection plates is positive relative to the cathode, and the disadvantages of current flowing to the deflection plates become manifest. According to one simple embodiment of the present invention, the advantages of this simpler construction are obtained and its disadvantages are avoided by making the deflection plates as planar grid-like electrodes and maintaining them at a potential lower than that of the cathode, and at the same time producing a lens effect between the region I now be described more fully by way of example,

with reference to the accompanying drawing, in

which:

Figure Us a diagrammatic view of a construction in which the grid-shaped deflection plates and the positive electrode are arranged behind each other;

Figure 2 is a plan view of the grid-shaped deflection plates and the positive electrode shown in Figure 1;

Figure 3 is a diagrammatic view, with the output anode omitted, 01 a form of construction in which the deflection grids and the positive electrode are arranged side by side.

Referring to the drawing, Figure l designates a cathode together with an electrode 2 which acts as a Wehnelt cylinder. In succession from the cathode at one end of the tube there is an accelerating or suction anode 3, next the grid-shaped negative deflection plates 4, constituted by spaced conductors or parallel wires 5, with the positive auxiliary electrodes 6 behind them; and finally, at the other end of the tube, the output anode comprising plates I and 8 separated by a blade-shaped electrode 9 and to a large extent surrounded bya screening electrode I 0. A supply battery i5 is connected through the load current to the output anode.

Figure 2 shows the relation of the grid-shaped deflection plates to the positive auxiliary electrodes 6,which are maintained slightly less positive than the accelerating anode 3 to produce in con junction with the accelerating'electrode a concentrating electron lens for further concentration of the discharge. The auxiliary electrodes 6, kept .positive by a connection 11, are mounted behind the deflection grids 4, which are given a negative bias potential relative to the'cathode by connections l8' and varied in relative potential by an input circuit IS.

The electrons emitted by the cathode I are united by the Wehnelt cylinder 2, in cooperation with the accelerating anode 3 and other electrodes, if present, to form a beam which traverses the space between the negative deflection grids 4 without loss of electrons to them, and finally impinges on the output anode. By the deflection grids 4 to which an alternating voltage is supplied by the input circuit I! the cathode beam is given a deflection so that it strikes alternately the output anode plates 1 and 8. A tube of this kind can be used advantageously in a push-pull circuit.

In the modification shown in Figure 3 each deflection plate and its auxiliary electrode are both grid-like and are coplanar, each deflection plate consisting of a row of small metal plates ll connected in parallel and each positive auxiliary electrode consisting of a number of conductors or wires i2 connected in parallel and interposed between and in the plane of the small plates of the corresponding deflection plate.

We claim:

1. An electron discharge device comprising an output anode, an electron source for producing a beam of electrons to said output anode, an apertured accelerating anode between said source and said output anode, a pair of planar grid-like deflection electrodes extending longitudinally between said anodes and spaced to permit the beam from said source to pass between said deflection electrodes to said output anode, auxiliary electrodes parallel to and coextensive with said deflection electrodes along the path of said beam and extending longitudinally of and outside said deflection electrodes, and means for maintaining said deflection electrodes at a negative potential and said accelerating anode and said a electrodes at different positive potentials with reference to said source to produce adjacent the side 01' said accelerating anode remote from said source a focusing fleld for the beam from said source.

2. An electron dischargedevice comprising anoutput anode, an electron source for producing a beam of electrons to said anode, a pair of gridlike parallel deflection electrodes spaced to permit the beam to pass between them to said anode, an accelerating anode between said source and said electrodes, a continuous sheet auxiliary'electrode extending alongside and parallel to each of said deflection electrodes throughout the length of said deflection electrodes along the path of said beam, and means for biasing said deflection electrodes at a negative potential and said auxiliary tween said source and said electrodes, a planar grid-like auxiliary electrode coplanar with each of said deflection electrodes and comprising a plurality of spaced parallel conductors and interleaved with said deflection electrodes, and means for biasing said deflection electrodes at a negative' potential and said auxiliary electrodes at a positive potential with reference to said source.

4. An electron discharge devicecomprising an output anode, an electron source for producing a beam of electrons to said output anode, an accelerating anode between said source and said output anode, a pair of parallel planar grid-like deflection electrodes spaced topermit the beam to pass between and lengthwise of said electrodes, a pair of auxiliary electrodes parallel to and coextensive withsaid deflection electrodes along the path of said beam for producing an electrostatic field extending through said deflection electrodes throughout their length, and means for maintaining said accelerating anode at a high positive potential, said auxiliary electrodes at a less positive potential, and said deflection plates at a negative potential with referenceto said source.

5. An electron discharge device comprising an output anode, an electron source for producing a beam of electrons to said output anode, an accelerating anode between said source and said output anode, a pair of continuous sheet auxiliary electrodes spaced to permit the beam to pass between and lengthwise of said electrodes, a pair of gridlike deflection electrodes parallel to and between said auxiliary electrodes and of substantially the same length as and coextensive with said auxiliary electrodes and spaced to permit said beam to pass between and lengthwise of said deflection electrodes, and means for maintaining said auxiliary electrodes at a positive potential and said deflection electrodes at a negative potential with refer- 55 ence to said source. 

